Why can concurrent engineering projects take so long and cost so much, despite our best efforts to use such apparently sensible techniques as multi-functional design teams, set-based design, and computer-aided collaborative design tools? Consider for example the Boeing 767-F redesign program. Some conflicts were not detected until long (days to months) after they had occurred, resulting in wasted design time, design rework, and often even scrapped tools and parts. It was estimated that roughly half of the labor budget was consumed dealing with changes and rework, and that roughly 25-30% of design decisions had to be re-worked. Since maintaining scheduled commitments was a priority, design rework often had to be done on a short flow-time basis that typically cost much more (estimates ranged as high as 50 times more) and sometimes resulted in reduced product quality. Conflict cascades that required as many as 15 iterations to finally produce a consistent design were not uncommon for some kinds of design changes. All this in the context of Boeing's industry-leading concurrent engineering practices. The dynamics of current collaborative design processes are thus daunting, and have led to reduced design quality, long design cycles, and needlessly high costs.

The emerging discipline of complex systems research offers a new and potentially powerful perspective on these problems, by attempting to understand the dynamics of distributed systems using such concepts as chaos, power laws, self-similarity, emergence, self-organization, networks, adaptation, evolution, and so on. It has proven to be quite fruitful, offering powerful and intriguing explanations and prescriptions for phenomena ranging from vehicle traffic to global economies to evolution to the weather.

This special issue collects five papers that apply the complex systems perspective to concurrent engineering. The papers by Klein et al., Ford et al. Loch et al. and Yassine et al. describe how we can use complex systems models to help understand and improve the emergent dynamics of concurrent engineering processes. The paper by Wallace et al. describes the kind of novel computing infrastructure that becomes necessary when supporting emergent concurrent engineering processes.

• Mark Klein, Hiroki Sayama, Peyman Faratin and Yaneer Bar-Yam
  The Dynamics of Collaborative Design: Insights From Complex Systems and Negotiation Research

• David N. Ford and John D. Sterman
  Iteration Management for Reduced Cycle Time in Concurrent Development Projects

• Christoph Loch, Jürgen Mihm and Arnd Huchsermeier
  Concurrent Engineering and Design Oscillations in Complex Engineering Projects

• Ali Yassine and Dan Braha
  Complex Concurrent Engineering and the Design Structure Matrix Method

• David Wallace, Elaine Yang and Nicola Senin
  Integrated Simulation and Design Synthesis

The Dynamics of Collaborative Design: Insights From Complex Systems and Negotiation Research
Mark Klein, Hiroki Sayama, Peyman Faratin and Yaneer Bar-Yam

Almost all complex artifacts nowadays, including physical artifacts such as airplanes, as well as informational artifacts such as software, organizations, business processes, plans and schedules, are defined via the interaction of many, sometimes thousands of participants, working on different elements of the design. This collaborative design process is typically expensive and time-consuming because strong interdependencies between design decisions make it difficult to converge on a single design that satisfies these dependencies and is acceptable to all participants. Recent research from the complex systems and negotiation literatures has much to offer to the understanding of the dynamics of this process. This paper reviews some of these insights and offers suggestions for improving collaborative design.

Iteration Management for Reduced Cycle Time in Concurrent Development Projects
David N. Ford and John D. Sterman

Successfully implementing concurrent development to reduce cycle time has proven difficult due to unanticipated interactions of process constraints and managerial decision-making. However, many theories and models addressing concurrent development treat either the technical aspects of development processes (e.g., precedence relationships and delays in discovering rework requirements) or the behavioral issues (e.g., creating effective cross-functional teams), but not their linkages. We argue that much of the complexity of concurrent development---and the implementation failures that plague many organizations---arise from the interactions between the technical and behavioral dimensions of projects. The often puzzling and dysfunctional dynamics of projects emerge from the feedbacks, time delays, nonlinearities, and other elements of complex systems created by these structures and interactions. We develop a dynamic project model that explicitly models these interactions to investigate the causes of the "90% syndrome," a common form of schedule failure in concurrent development. We find that increasing concurrence and the common propensity of workers to conceal required changes from other development team members aggravate the syndrome and disproportionately degrade schedule performance and project quality. We discuss the role of behavior in concurrent development failure and explore iteration management policies to improve performance in concurrent development projects.

Concurrent Engineering and Design Oscillations in Complex Engineering Projects
Christoph Loch, Jürgen Mihm and Arnd Huchsermeier

Coordination among many interdependent actors is key activity in complex product development projects. The challenge is made more difficult in concurrent engineering processes, as more activities happen in parallel and interact. This coordination becomes progressively more difficult with project size. We do not yet sufficiently understand whether this effect can be controlled with frequent and rich communication among project members, or whether it is inevitable. Recent work in complexity theory suggests that a project might form a ``rugged landscape'', for which performance deterioration with system size is inevitable.

This article builds a mathematical model of a complex concurrent design project. The model explicitly represents local component decisions, as well as component interactions in determining system performance. The model shows, first, how a rugged performance landscape arises from simple components with single-peaked performance functions, if the components are interdependent.

Second, we characterize the dynamic behavior of the system analytically and with simulations. We show under which circumstances it exhibits performance oscillations or divergence to design solutions with low performance. Third, we derive classes of managerial actions available to improve performance dynamics, such as limiting the ``effective'' system size of fully interdependent components, modularity, and cooperation among designers. We also show how ``satisficing'', or a willingness to forego the last few percent of optimization at the component level, may yield a disproportionally large improvement in the design completion time.

Complex Concurrent Engineering and the Design Structure Matrix Method
Ali Yassine and Dan Braha

Concurrent engineering (CE) principles have considerably matured over the last decade. However, many companies still face enormous challenges when implementing and managing CE practices. This is due to the increased complexity of engineering products and processes, on one hand, and the lack of corresponding CE models and tools, on the other hand.

This paper focuses on four critical problems that challenge management while implementing concurrent engineering (CE) in complex product development (PD) projects. We refer to these problems as: iteration, overlapping, decomposition & integration, and convergence problems. We describe these problems proposing a unified modeling and solution approach based on the design structure matrix (DSM) method, which is an information exchange model that allows managers to represent complex task relationships to better plan and manage CE initiatives.

Integrated Simulation and Design Synthesis
David Wallace, Elaine Yang and Nicola Senin

The potential benefits of mathematically predicting and analyzing the integrated behavior of product concepts throughout the design synthesis cycle are widely recognized. Better up-front integrated design will not only reduce development time and cost, but also will yield higher quality products with improved performance. Many academic researchers and companies have attempted to develop integrated simulation environments, and it has been observed consistently that significant difficulties arise because of the large scale, complexity, rate-of-change, heterogeneity, and proprietary barriers associated with product design synthesis. However, the focus of most integration efforts has been on enabling technology, while the process of how integrated systems are constructed has not been questioned.

The literature acknowledges that it is very difficult to represent and structure emergent processes using explicit system definition techniques like those that have been almost universally adopted. The belief that design synthesis is an emergent system definition process drives the search for a different approach to building integrated design simulations. Inspired by a vision of the World-Wide Web as an emergent informationnetwork building environment, a World-Wide Simulation Web concept is proposed for defining an emergent, integrated, simulation-building environment. Participants should be able to make interfaces to local sub-system simulations parametrically operable and accessible over the Internet. Furthermore, any participant should be able to make relationships between parameters in different simulation interfaces or to create additional models that bridge interfaces to different simulations distributed over the Internet.

The DOME (Distributed Object-based Modeling Environment) project has developed a software infrastructure for the purpose of refining and testing emergent simulation definition concepts. A federating solving mechanism has been developed that allows local solvers to respond in a manner that is consistent with the overall system structure even though there is no centralized coordination of the simulation. Results from several pilot studies support the belief that an emergent, decentralized approach to building integrated simulations can resolve many of the difficulties associated with integrated system simulation.